False twisting apparatus

ABSTRACT

Apparatus for false twisting thread has a rotary twisting member with a composite thread contacting surface which includes separate annular portions having relatively high and relatively low coefficients of friction. Thread is guided by the low friction annular portions of the twisting member with respect to the high friction annular portions where twisting forces are imparted to the thread. Multiple twisting members are arranged in sequence along the direction of movement of the thread to provide predetermined twist characteristics to the thread.

U United States Patent l 1 [111 3,901,01 1

Schuster Aug. 26, 1975 [54] FALSE TWISTING APPARATUS 3.537.250 11/1970MacKintosh 57/774 3,656.290 4 1972 K z i. 57 77.4 [75] Inventor:Friedrich Schuster, Hammelburg, 3 762 149 51973 57274 Germany 3,777,46712/1973 Enncking 57/77.4

[73} Assignee: Kugelfischer Georg Schafer & C0.,

Schweinfurt. Germany Primary Examiner-Donald E. Watkins Filed: Feb 11974 Attorney. Agent, or Fzrm-Edward R. Wemgram 21 A l. No.: 441,209 I 1pp 57 ABSTRACT [30] Foreign Application Priority Data Apparatus forfalse twisting thread has a rotary twistmg member with a compositethread contacting sur- 7 Germany 306853 face which includes separateannular portions having 1973 3359788 relatively high and relatively lowcoefficients 0f fric- 1974 Germany 400239 tion. Thread is guided by thelow friction annular por- Cl 7 77 tions of the twisting member withrespect to the high [52] i friction annular portions where twistingforces are im- [511 'f 7 l parted to the thread. Multiple twistingmembers are [58] new 0 5 5 arranged in sequence along the direction ofmovement of the thread to provide predetermined twist charac- [56]References Cited teristics t0 the thread.

UNITED STATES PATENTS 2,939,269 6/1960 Dobson 57/774 20 qalms, 18 DrawmgFlgures L7 K T a/ H 49 A 5 PATENTED AUG 2 6 I975 Ix" SiiL ETBUFG FALSETWISTING APPARATUS BACKGROUND OF THE INVENTION:

1. Field of the Invention This invention relates to apparatus fortwisting threads and, more particularly, to apparatus for false twistingthreads by passing the threads in frictional contact over rotatingfrictional surfaces.

2. Description of the Prior Art In friction-type false-twistingapparatus, the thread to be false-twisted is guided past one or morerotary twisting members, such as rotating friction discs, so as to berolled around on them. The peripheral surface of each friction discwhich engages the thread to be falsetwisted is made of resilientmaterial having a suitably high coefficient of friction as a rulepolyurethane of predetermined known hardness. The contact surface is asa rule cylindrical or formed with an arcuate cross section.

Devices with friction discs for friction false-twisting syntheticthreads for crimping or texturing them are known in various forms. Thefriction discs are arranged in spaced relation on a rotatably mountedspindle or on two or three substantially mutually parallel rotatablymounted spindles. (See, for example, US. Pat. No. 3,327,463, French Pat.No. 1,261,747, British Pat. No. 854,781, or West German Ausslegerschrift(DAS) 1,222,826).

In the devices having two or three spindles, the friction discs on eachspindle generally overlap the friction discs on the other spindle or theother two spindles. All the spindles are driven in the same direction ofrota tion. In devices having two spindles, the thread to befalse-twisted can be guided to pass in the plane containing the axes ofthe two spindles between the two axially oppositely mutually offsetpairs of discs of the two spinclles (see French Pat. No. 1,261,747) or,alternatively, to run in the wedge-shaped gap between the two sets offriction discs on the two spindles (see British Pat. No. 854,781).

In devices having three spindles, it is known to arrange them so thatthey form, in plan view, the corners of a substantially equilateraltriangle, so that the thread to be false-twisted passes between themutually overlapping friction discs in a zig-zag path (see West GermanDAS 1,222,826).

In the friction discs known up to now, the whole surface which is to bein contact with the thread to be false-twisted is made from a materialhaving a suitably high coefficient of friction with respect to thethread. The thread is urged against the contact surface and rolls uponit. In order to be able to false-twist the thread satisfactorily withoutsubjecting the thread to unacceptably high tension loads which couldlead to breakage of the thread, the thread must exactly follow the rightpath past the friction discs which impart the false twist, and thefriction disc must rotate at the same peripheral speed at all points ofcontact with the thread. These requirements contradict one another.

In the known friction discs, in order to achieve satisfactory impartingof the false twist, in particular to avoid breakage of the thread, veryhigh standards have been set with regard to accuracy of manufacture andassembly, and adjustment of the equipment, with consideration given tothe characteristics of the particular thread to be false-twisted. In thecase of devices having mutually overlapping friction discs, thetolerances, es-

pecially those for the mutual overlap, disc thickness and disc diameterand for the axial spacing between each adjacent pair of discs areextremely small and, therefore, difficult to maintain in large-scaleproduction of this apparatus. Further, operation of these devices hasshown them to be largely incapable of maintaining the tolerancesnecessary for separate machines to provide satisfactory uniform qualityof false twist for similar threads, while keeping thread breakage withinpractical limits.

In friction false twisting, rotary twisting members other than frictiondiscs are also used. Frequently, friction sleeves are used through whichthe thread to be false-twisted is guided so as to be in rolling contactwith either the whole inner surface of the sleeve bore or simply in theregion of the two mouths of the sleeve bore, the overall contact surfacebeing made of a material having a high coefficient of friction forimparting the false twist, as shown in West German (DSA) 1,205,652, andWest German offenlegungsschrift (DT- OS) 2,104,255.

SUMMARY OF THE INVENTION To overcome the problems set forth above, thepresent invention provides apparatus for false twisting thread includinga rotary twisting member having separate annular portions withrelatively high and relatively low coefficients of friction. Theseparate annular portions form a composite thread contacting surfacewith the low friction annular portion guiding the thread with respect tothe high friction portion where twisting of the thread occurs. Relativeposition and shape of the high and low friction annular portions of thethread contacting surface comprises uniform relative velocity at allpoints of contact between the high friction annular portion and thethread.

In view of the above, it is an object of the present invention toprovide apparatus for false twisting thread, which has a compositethread contacting surface with separate portions for twisitng the threadand for guiding the thread.

Another object of the present invention is to provide apparatus forfalse twisting thread which produces constant relative speed between thethread twisting surface and the thread along all points of contactbetween-the friction surface and the thread.

It is a further object of the present invention to provide apparatus forfalse twisting thread, in which guide portions of the thread contactingsurfaces are made of relatively low friction material.

Still another object of the' present invention is to provide apparatusfor false twisting thread which avoids putting unacceptably highstresses on the threads.

It is yet another object of the present invention to provide apparatusfor false twisting thread which can be manufactured, assembled, andoperated with relatively large dimensional tolerances and still providesatisfactory performance.

Another object of the present invention is to provide apparatus forfalse twisting thread which will provide constant and uniform twistingcharacteristics on the thread processed by the apparatus.

It is still another object of the present invention to provide apparatusfor false twisting thread which has a composite thread contactingsurface with a separate thread twisting portion that rotates at arelatively constant peripheral speed, regardless of the overall shape ofthe thread contacting surface.

A further object of the present invention is to provide apparatus forfalse twisting thread which minimizes breakage of threads processed bythe apparatus.

Yet another object of the present invention is to provide apparatus forfalse twisting thread which allows the thread to exactly follow theproper path past the rotary twist members.

Still another object of the present invention is to provide apparatusfor false twisting thread which requires relatively large dimensionaltolerances that can easily be maintained during operation of theequipment.

It is another object of the present invention to provide apparatus forfalse twisting thread which can operate with a minimum of maintenanceand adjustment.

Other objects and advantages will be apparent from the followingdescription of embodiments of the invention, and the novel features willbe particularly pointed out hereinafter in connection with the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is a side view of a conventional friction disc for friction falsetwisting synthetic threads.

FIG. 2 is a view from above looking at a friction false twisting devicewith at least three mutually overlapping friction discs. I

FIG. 3 is a cross section through the rim of the friction disc of FIG.1.

FIG. 4 shows diagrammatically the construction of the shape of the crosssection of the convex contact surface of a friction disc according tothe invention for the device of FIG. 2.

FIG. 5 is a longitudinal section along the line VV in FIG. 2 through aset of friction discs of a device according to FIG. 2.

FIG. 6 is a plan view of a friction disc according to the presentinvention, made of a material having a low coefficient of friction, intowhich portion made from a material of high coefficient of friction isincorporated.

FIGS. 7 to 12 each show the portion A of FIG. 5, with a differentconstruction for the friction discs.

FIG. 13 is a side view, partially sectioned, of one embodiment of thefalse twisting device built in accordance with the present invention.

FIG. 14 is a side view, to a larger scale, partially sectioned, of afriction disc used in the device of FIG. 13.

FIG. 15 is a plan view of the embodiment of the invention shown in FIG.13.

FIGS. 16 and 17 each show a side view of another embodiment of theinvention, only the friction discs being shown in the mutuallyoverlapping region.

FIG. 18 is a side view, partially sectioned, of another embodiemnt ofthe invention, having a friction cylinder.

In FIG. 1, there is illustrated by way of example the engagement of athread 1 to be false-twisted with a friction disc 2 of a device forfriction false twisting of synthetic threads according to FIG. 2. Such adevice comprises three sets 3, 4 and 5, of friction discs of which theaxes of rotation are substantially parallel to one another and, in planview, form the corners of an approximately equilateral triangle. Thefriction discs of each set 3, 4 and 5 overlap the friction discs of theother two.

sets 4 and 5 or 3 and 5 or 3 and 4. The thread 1 to be false-twisted isin contact with the friction discs of all three sets 3, 4 and 5.

The thread 1 is pressed against each friction disc 2 and in fact againsta contact surface 6 of each disc so as to roll on that surface. Thethread 1 forms an angle alpha with the plane of rotation of the frictiondisc 2. The point of the contact surface 6 of the disc 2 having thegreatest outside diameter moves at a peripheral speed of V By virtue ofthe tension T in the thread, dependent chiefly on the take-up equipment,the thread 1 is pressed against the contact surface 6 of the disc 2 witha certain force, not shown in FIG. 1, directed perpendicular to theplane of the drawing, resulting in a force F,, directed tangentiallywith respect of the contact surface 6. This can be resolved into twocomponents, namely a force F perpendicular to the longitudinal axis ofthe thread 1 and a force F,, in the direction of this longitudinal axis.The force F has a twistimparting action on the thread 1, i.e. it rotatesthe thread 1 about its longitudinal axis. The force F depends chiefly onthe peripheral speed V The force F A pulls the thread 1 past the disc 2in the direction of the arrow P, i.e. it assists the action of thetake-up equipment.

If the angle alpha is suitable, it is in fact possible for the threadtension T. to be smaller than the thread tension T which can never bethe case under normal conditions, as with the disc 2 stationary, whenthe thread tension T is always greater than the thread tension T,. Thismeans that the thread tension ratio T /T can be controlled veryaccurately with the aid of the angle alpha and the peripheral speed V Inthis way, it is possible, with sensitive threads 1, to keep the threadtension and therefore also the number of thread breakages withinacceptable limits. From this theoretical reasoning, it follows that theangle alpha and the peripheral speed V of each friction disc 2 or otherrotary twisting member are the deciding factors for economicallyfalse-twisting threads to crimp them. By means of the invention, thesetwo important controlling factors can be controlled as accurately aspossible and in fact can be maintained without narrow tolerances, sothat despite the friction discs being easier to manufacture, theimparting of a false twist and accordingly the crimping are achievedwith a uniformly high quality.

In order to maintain the angle alpha as accurately as possible it isbest for the thread 1, in its passage through a friction false twistingdevice according to FIG. 2, to move along a helical line having asubstantially constant angle, i.e. it runs helically over the imaginarycylinder 7 in FIG. 2. Tolerances on the diameter of the discs or in thespacing between each adjacent pair of discs 2 have a smaller influenceon the angle alpha than when the thread 1 passes over sharp edgesbetween the overlapping discs 2, because these tolerances and therebyalso the angle alpha change very markedly, and, since the variation ofthe thread tension follows an exponential function, this exerts a muchgreater influence on the thread 1.

In particular, in the example described with overlapping discs, wherethe thread 1 to be false twisted passes over sharp edges, this thread isvery heavily loaded, so that many breakages arise and in practice reallyfine yarn cannot be handled at all with such friction discs.

In order to acheive a passage of the thread between the discs 2 along ahelical path, the path extending along an imaginary cylinder 7 (FIG. 2)the form of the cross section of the contact surfaces 6 which is shownin FIG. 4 is necessary.

FIG. 4 shows how the shape of the cross section of the contact surface6, i.e. the profile 8, can be built up point by point where the diameterD of the mutually overlapping friction discs 2, the spacing A andthereby the overlap B between three adjacent discs 2, and the discthickness H and the axial spacing AH between each adjacent pair offriction discs 2 are known. The procedure is as follows first a circleis drawn having a diameter D and then within this there is drawn acircle having a radius B, so that the two circles touch one anothertangentially. Then the outer one-third arc of the circle having theradius B is divided uniformly and through each of the resulting pointsX1, X2 there is struck a respective circle which is concentric with thecircle of diameter D. Two lines 8 and 9 are drawn in, H AH apart, theselines being parallel to a common radius of the circle of diameter D. Onthe line 9 the portion C (21rTTB)/3 is cut off and divided into the samenumber of portions as the outer one-third arc of the circle of radius B.Through the resulting points X1, X2 perpendicular lines are drawn. Theuppermost point of the line 9 in FIG. 4 and the lowermost point on theline 8 are connected by an inclined line 10. Through the points ofintersection of this line 10 with the above mentioned perpendicularlines parallel straight lines 11 are drawn. Each such line 11 cuts theassociated circle around the center M at a predetermined point X1" orX2" by connecting up these last-mentioned points we obtain the profile8.

The ideal cross section of the contact surface 6 in accordance with theprofile 8 can be closely approximated by a cross section which is easierto produce, for example by an arcuately curved cross section in accordance with FIG. 3.

It follows from what has been said above that for a predetermined anglealpha the contact surface 6 of the friction disc 2 must have apredetermined cross section shape which does not depart significantlyfrom the theoretical shape set out above. Otherwise the thread 1 isoverloaded by the sharp change in direction in the thread path.

As shown in FIG. 3, in known friction discs a material having a suitablyhigh coefficient of friction is present over the entire contact surface6 that engages the thread I. The surface 6 has a radius R, which variesover the thickness H of the disc, and consequently produces a varyingperipheral speed V This speed variation conflicts with the exactimparting of a false twist since for this purpose the peripheral speed Vof the contact surface 6 should be of uniform magnitude over the wholeregion of the twist-imparting contact surface 6, as explained above.

According to the invention in particular in friction discs 2 forfriction false twisting devices according to FIG. 2 the contact surface6, which preferably has a cross sectional shape according to FIGS. 4 or3, is divided into regions of different coefficient of friction, whichare mutually adjacent in the direction of the thickness H of the discand extend around the entire periphery of the disc. The region of highercoefficient of friction serves to impart the false twist, and the otherregion of lower coefficient of friction serves to guide the thread. Inthe region of higher coefficient of friction the peripheral speed issubstantially uniform so that exact imparting of the false twist isachieved.

In devices like those shown in FIG. 2, the shapes of friction discaccording to the invention shown in FIGS. 7 to 9 are particularlysuitable, the embodiment of FIG. 9 being the preferred one. In theembodiment shown in FIG. 7, the disc 2 is made of material of lowcoefficient of friction. An annular groove 13 is machined to receive aring 14 of material of high coefficient of friction. In the embodimentshown in FIG. 8, the disc is made of material of lower coefficient offriction, and

has an outer annular flange 15. A ring 14 of higher coefficient offriction is positioned between flange l5 and a ring 16 of material oflower coefficient friction. The ring 16 can be made of the same materialas the disc 2. The embodiment shown in FIG. 9 differs from that of FIG.7 in that the disc 2 has, in addition to the annular groove 13, a ringof axial holes 17, as shown in FIG. 6. These communicate with the groove13 and are likewise filled with material of higher coefficient offriction, for example, by the material which was cast in place, and thenmachined to obtain the desired shape for the contact surface 6.

FIGS. 10 and 11 show embodiments of the friction discs accordingto theinvention with asymmetrical distribution in the contact surface 6 of theregions of different coefficient of friction. The overall shape of thecross section in the embodiment of FIG. 10 is symmetrical, while beingasymmetrical in the embodiment shown in FIG. 11. In the embodiment ofFIG. 10 the disc 2 is made of material of lower coefficient of frictionand has a side annular flange 15 and a second annular flange 18 with aninwardly directed annular shoulder 19 and a ring of axial holes 17through flange 18. The flange 18 is embedded, by casting, in material ofhigher coefficient of friction. The cross sectional shape of the contactsurface 6 is obtained by subsequent machining.

In the embodiment shown in FIG. 11 the friction disc 2, made of materialhaving a lower coefficient of friction, has a central annular flange 18with respective inwardly directed annular shoulders 19 on both sides andwith a ring of axial holes 17. The flange 18 is embedded, by casting, inmaterial of higher coefficient of friction, which also passes throughthe holes 17. The high friction material is shaped asymmetrically at theperiphery of the disc. On the side of the disc 2 where the surface 6,which is of relatively small radius meets the flat face of the disc 2,there is provided a ring 20 of material of low coefficient of friction.

The friction discs 2 according to FIGS. 7 to 11 each have a hub 21 asshown in FIG. 5, by which they are secured on a spindle 22. As shown inFIG. 5 three discs 2 form the friction disc sets 3, 4 or 5 in the deviceaccording to FIG. 2. The discs 2 are arranged one above the other on thespindle 22, a predetermined spacing 23 being provided between eachadjacent pair of discs 2 in order to prevent undesired deformation ofthe spindle 22.

The friction discs of the type shown in FIGS. 10 and 11, when mounted ina friction false twisting device, such as the type shown in FIG. 2, arepreferably mounted so that the thread to be false-twisted first comesinto contact with the surface 6 in the region of higher frictional valueand leaves from the region of lower coefficient of friction.

The invention also provides advantages if used in friction discs havingthe shape shown in FIG. 12, where a substantially cylindrical contactsurface 6 meets the two faces of the disc at small radii of curvature.

The material of lower coefficient of friction can be a metal, forexample brass, steel or aluminum, or a synthetic resin, for example aresin based on a polyoxymethylene, polymer, known under the Trade MarkHostaform or manufactured by polymerization from water-free CH O, knownunder the Trade Name Delrin. The material of higher coefficient offriction can for example be a polyurethane or a special synthetic rubberknown under the Trade Mark Perbunan.

The friction discs according to the present invention are particularlyadvantageous in that the thread to be false-twisted is subjected tosignificantly lower loads during the false twisting. In the knownfriction discs, the entire contact surface has a frictional action onthe thread. Since the contact surface, as shown in FIG. 3, has a radiusR1 which varies over the thickness H of the disc, the peripheral speed Vwill vary over the thickness H and, accordingly, the forces on thethread will differ at different points of the contact surface becausethe thread can only travel at a single speed. All the other peripheralspeeds which differ from the spped of the thread only cause additionalfriction of the disc on the thread and subject it to loads. Moreover itis difficult to achieve an exact well defined false twist.

In addition, the friction disc according to the present invention isdistinguished by the feature that it is easier and cheaper to produce inview of the greater tolerances that are permitted on its dimensions.Further, in view of the greater permitted tolerances, the friction discis easier and cheaper to assemble and adjust with regard to its positionrelative to the adjacent disc or discs. This ease of assembly andadjustment is particularly significant when replacement of frictiondiscs in friction false twisting apparatus is necessary in the course ofrepairs.

FIG. 13 shows a three-spindle, multi-friction disc false twistingdevice. Three spindles 32 are mounted in a baseplate 31. These arearranged parallel to each other and form in plan view the corners of anequilateral triangle, as shown in FIG. 15. Each spindle 32 is providedwith an encapsulated bearing 33 secured to the baseplate 31 by means ofa nut 34. On the lower end in FIG. 13 each spindle 32 is in additionprovided with an externally toothed gear 35. All three gears 35 aresurrounded by a common internally toothed belt 36. Accordingly, inoperation, the spindles 32 all run in the same direction of rotation, asshown in FIG. 5.

On each spindle 32 there is mounted a set of three friction discs 37,each having a hub and an annular flange at one end of the hub. The discs37 of each set are secured next to one another on a common locatingsleeve 38. The locating sleeve 38 is fitted onto the associated spindle32 together with at least one spacing ring 39 and connected to it so asto rotate with it by means of an annular disc 40 and a screw 41. On theopposite side from the disc 40 and the screw 41 the locating sleeve 38engages against an abutment ring 42 which is provided on the spindle 32.

The mutually identical sets of friction discs are arranged on therespective associated spindle 32 with the discs 37 at different axialpositions. This is achieved by the spacing rings 39. On the lefthandspindle 32 in FIG. 13 such a spacing ring 39 is provided above the setof discs, and the same applies to the righthand spindle 32 except thathere the set of friction discs is inverted, i.e. standing on its head.On the middle spindle 32 there are provided two spacing rings 39, namelya taller one below and a shallower one above the set of friction discs,which set of discs is itself arranged the same way up as on the lefthandspindle 32.

The friction discs on the three spindles thus mutually overlap, and inoperation they rotate in the same direction, for example in thedirection of the arrow 43 in FIG. 15. The thread 45 which runs in thedirection of the arrow 44, i.e. from above in a downward directionthrough the device, is therefore provided with a Z twist.

It follows azig-zag path past the friction discs 37, engaging againstthem, to leave the device through a stationary anti-ballooning tube 46.The anti-ballooning tube 46 extends through the baseplate 311 and issecured to it in the middle of the above-mentioned equilateral triangleof spindles.

The thread 45 is pressed against each of the friction discs, in factagainst a contact surface 47 of each disc, in order to roll upon it. Thethread 45 makes an angle alpha with the plane of the disc 37. By virtueof the thread tension T, which is dependent chiefly on the take-uparrangements, the thread 45 is urged against the contact surface 47 ofthe disc 37 with a force which is not shown in FIG. 14 but which actsperpendicular to the plane of the drawing in that figure, so that thereresults the force F T directed tangentially with respect to the surface47. This force can be resolved into two components, a force Fperpendicular to the lonngitudinal axis of the thread 45, and a force FA in the direction of this longitudinal axis of the thread. The force Fhas a twisting action on the thread 45, i.e. it turns the thread 45about its own longitudinal axis. The force F,, draws the thread 45 inthe direction of the arrow 44 against the disc 37 in question, i.e. itassists the action of the take-up rollers.

The contact surface 47 is divided along its width H into separateregions having different coefficients of friction. Each of the separateregions extend around the entire periphery of the disc. As discussedabove, to provide the separate regions, the disc 37 is made of materialof lower coefficient of friction, and an annular groove 48 is machinedin the periphery to receive a ring 49 of a material having a highercoefficient of friction. The region of the contact surface 47 havinghigher coefficient of friction formed by the ring 49 serves to impartthe false twist and the two adjoining regions of low coefficient offriction serve to feed the thread. In the region of higher coefficinetof friction the peripheral speed of the contact surface 47 isapproximately uniform, so that an exact imparting of the false twist isachieved.

According to the invention the different friction discs 37 in the deviceof FIG. 13 have different coefficients of friction for imparting thefalse twist. The coefficient of friction of the rings 49 increases fromthe thread inlet disc 37 to the thread outlet disc 37". All nine discs37 have the same mutual spacing A and have the same outside diameter Dand the same thickness H.

The embodiment of the device shown in FIG. 16 differs from that of FIG.13. All of the high coefficient of friction rings 49 have the samecoefficient of friction with respect to the thread 45 to befalse-twisted, for imparting the false twist, and the friction discs 37have different thicknesses H which increase from the thread inlet disc37 to the thread outlet disc 37". Accordingly, in the device shown inFIG. 16, the first three, the three intermediate and the three lastdiscs 37 each have the same thickness I-I, i.e. the three sets of discson the three spindles 32 are identical.

The embodiment of the device shown in FIG. 17 differs from that of FIG.13 in that all the rings 49 have the same coefficient of friction withrespect to the thread 45 but the discs 37 have different mutual spacingsA, and the spacings A increase from the thread inlet disc 37 to thethread outlet disc 37". Again the arrangement can be such that the threesets of friction discs on the three spindles 32 are identical.

The features present in the embodiments of FIGS. l3, l6 and 17 could becombined together.

Another embodiment of a false twisting device uses a rotary twistingdevice of a friction cylinder instead of a friction disc. Thisembodiment of a false twisting device is shown in FIG. 18, where thereare pivotally or rotatably mounted in a carrier 51 a spindle 52 with twothread guides 53 on its two ends and a friction cylinder 54 parallel toit. The bearing of the cylinder 54 is incorporated in a capsule 55secured to the carrier 51 by means of a nut 56 screwed onto it.

The cylinder 54 is made up of a tube 57 and two heads 58 mounted on itstwo ends. Secured to the tube 57 is a sleeve 59 engaged by a drivingbelt (not shown) to drive the cylinder 54.

Each head has an annular insert 60 with an annular twisting 61 in whichis provided a ring of material 62 having a higher coefficient offriction than the material of the insert 60. Thus in the relativelynarrow region of the annular groove 61 the convexly curved contactsurface 63 of each insert 60 has, with respect to the thread to befalse-twisted, a higher coefficient of friction than in the remainingregions.

In FIG. 18 there is shown in full lines that pivotal po sition of thespindle 52 in the carrier 51 in which the two aligned thread guides 53are lined up with the longitudinal bore 64 of the cylinder 54, that isto say of the tube 57. This is the position in which the respectivethread to be false-twisted is threaded in. The spindle 52 can be swungfrom this position into the operative position in which the threadguides 53 take up the positions shown in broken lines. In this positionthe thread runs through the cylinder 54 along the path 63 shown inbroken lines.

The thread thus engages against the contact surfaces 63 of both heads58. It rolls on these contact surfaces 63 when the cylinder 54 is set inrotation, in order to false-twist the thread. As that region of eachsurface 63 is kept relatively small, in which there is frictionalcontact between thread and cylinder 54 necessary for twisting thethread, the thread is not dragged at varying peripheral velocities.Further, the resistance which the contact surfaces 63 offers throughfriction to oppose the passage of the thread through the cylinder 54 iskept to the minimum possible value.

It will be understood that various changes in the details, materials andarrangements of parts which have been herein described and illustratedin order to explain the nature of the invention may be made by thoseskilled in the art within the principle and scope of the invention, asexpressed in the appended claims.

What is claimed is:

1. A rotary twisting member for imparting a twisting force to threads incontact with the twisting member when it rotates, comprising:

flange means extending in the plane of rotation of said twisting member;

an annular thread contacting surface having a plurality of annularsegments peripherally disposed on said flange means including:

an annular segment formed from material having a relatively highcoefficient of friction, adapted to impart twisting forces to thread incontact with said segment;

an annular segment formed from material having a relatively lowcoefficient of friction adapted for guiding a thread in contact withsaid segment.

2. A rotary twisting member according to claim 1 wherein the annularsegment formed from material having relatively high coefficient offriction is disposed on the thread contacting surface at the point ofmaximum velocity of said thread contacting surface as it rotates.

3. A rotary twisting member according to claim 2 wherein said annularsegments formed from material having relatively low coefficient offriction are disposed on opposite sides of said annular segment formedfrom material having a relatively high coefficient of friction.

4. A rotary twisting member according to claim 3 wherein said contactingsurface is symmetrically shaped with relation to the annular segmentformed from material of a relatively high coefficient of material.

5. A rotary twisting member according to claim 2 wherein said contactingsurface is convex in cross section.

6. A rotary twisting member according to claim 2 wherein said contactingsurface is cylindrical in cross section.

7. A rotary twisting member according to claim 2 wherein said rotarytwisting member includes a friction disc comprising:

flange means extending in the plane of rotation of said rotary twistingmeans;

said contact surface being formed on the peripheral edge of said flangemeans.

8. A rotary twisting member according to claim 7 wherein said annularsegments formed from material having relatively low coefficient offriction are disposed on opposite sides of said annular segment formedfrom material having a relatively high coefficient of friction.

9. A rotary twisting member according to claim 8 wherein said contactingsurface is symmetrically shaped with relation to the annular segmentformed from material made of relatively high coefficient of material.

10. A rotary twisting member according to claim 7 wherein saidcontacting surface is convex and is asymmetrically formed with respectto said annular segment formedfrom material having a relatively highcoefficient of friction.

1 l. A rotary twisting member for imparting a twisting force to threadsin contact with the twisting member when it rotates comprising:

a tubular section for the passage of thread to be twisted;

a mouth at each end of said tubular section;

an annular thread contacting surface having a plurality of annularsegments formed on each of said mouths; said annular thread contactingsurface including:

an annular segment formed from material having a relatively highcoefficient of friction, adapted to impart twisting forces to thread incontact with said segment; an annular segment formed from materialhaving a relatively low coefficient of friction adapted for guiding athread in contact with said segment; means rotatably supporting saidtubular section; thread guide means disposed adjacent each mouth of saidrotary twisting member; said thread guide means connected to said meansrotatably supporting said tubular section. 12. A rotary twisting memberaccording to claim 11 wherein said annular segments formed from materialhaving relatively low coefficient of friction are disposed on oppositesides of said annular segment formed from material having a relativelyhigh coefficient of friction.

13. A rotary twisting member according to claim 12 wherein saidcontacting surface is convex in cross section.

14. A device for false twisting threads comprising:

a plurality of rotary twisting members for imparting a twisting force tothreads in contact with the twisting member when it rotates, each ofsaid rotary twisting members comprising: flange means extending in theplane of rotation of said twisting member;

an annular thread contacting surface having a plurality of annularsegments peripherally disposed on said flange means including:

an annular segment formed from material having a relatively highcoefficient of friction, adapted to impart twisting forces to thread incontact with said segment;

an' annular segment formed from material having a relatively lowcoefficient of friction adapted for guiding a thread in contact withsaid segment;

said annular thread contacting surfaces of said plurality of rotarytwisitng members having parallel axis of rotation.

15. The device for false twisting threads according to claim 14 wherein:

said plurality of friction disc comprise:

at least three mutually overlapping friction discs;

the axis of rotation of said three mutually overlapping friction discsdisposed to form the corners of a substantially equilateral triangle;

the contact surfaces of said plurality of friction discs coacting tocause thread passing through said false twisting device to travel on asubstantially helical path.

16. The device for false twisting threads according to claim 15 furthercomprising:

a spindle;

said plurality of rotary twisting members disposed in spaced relation onsaid spindle; and

means to synchronously drive said plurality of rotary twisting memberson said spindle.

17. The device for false twisting threads according to claim 16 whereinsaid plurality of rotary twisting members are disposed on three spindlespositioned to form, in the plan view, a substantially equilateraltriangle.

18. The device for false twisting threads according to claim 16 whereinthe coefficient of friction of said annular segments formed frommaterial of a relatively high coefficient of friction varies inpredetermined relationship for said friction discs spaced along saidspindle.

19. The device for false twisting threads according to claim 17 whereinthe spacing between said friction discs spaced on said spindle varies ina predetermined relationship.

20. The device for false twisting threads according to claim 17 whereinthe thickness of said flange means of said friction discs mounted inspaced relation on said common spindle varies along the spindle inaccordance with a predetermined relationship. 1

1. A rotary twisting member for imparting a twisting force to threads incontact with the twisting member when it rotates, comprising: flangemeans extending in the plane of rotation of said twisting member; anannular thread contacting surface having a plurality of annular segmentsperipherally disposed on said flange means including: an annular segmentformed from material having a relatively high coefficient of friction,adapted to impart twisting forces to thread in contact with saidsegment; an annular segment formed from material having a relatively lowcoefficient of friction adapted for guiding a thread in contact withsaid segment.
 2. A rotary twisting member according to claim 1 whereinthe annular segment formed from material having relatively highcoefficient of friction is disposed on the thread contacting surface atthe point of maximum velocity of said thread contacting surface as itrotates.
 3. A rotary twisting member according to claim 2 wherein saidannular segments formed from material having relatively low coefficientof friction are disposed on opposite sides of said annular segmentformed from material having a relatively high coefficient of friction.4. A rotary twisting member according to claim 3 wherein said contactingsurface is symmetrically shaped with relation to the annular segmentformed from material of a relatively high coefficient of material.
 5. Arotary twisting member according to claim 2 wherein said contactingsurface is convex in cross section.
 6. A rotary twisting memberaccording to claim 2 wherein said contacting surface is cylindrical incross section.
 7. A rotary twisting member according to claim 2 whereinsaid rotary twisting member includes a friction disc comprising: flangemeans extending in the plane of rotation of said rotary twisting means;said contact surface being formed on the peripheral edge of said flangemeans.
 8. A rotary twisting member according to claim 7 wherein saidannular segments formed from material having relatively low coefficientof friction are disposed on opposite sides of said annular segmentformed from material having a relatively high coefficient of friction.9. A rotary twisting member according to claim 8 wherein said contactingsurface is symmetrically shaped with relation to the annular segmentformed from material made of relatively high coefficient of material.10. A rotary twisting member according to claim 7 wherein saidcontacting surface is convex and is asymmetrically formed with respectto said annular segment formed from material having a relatively highcoefficient of friction.
 11. A rotary twisting member for imparting atwisting force to threads in contact with the twisting member when itrotates comprising: a tubular section for the passage of thread to betwisted; a mouth at each end of said tubular section; an annular threadcontacting surface having a plurality of annular segments formed on eachof said mouths; said annular thread contacting surface including: anannular segment formed from material having a relatively highcoefficient of friction, adapted to impart twisting forces to thread incontact with said segment; an annular segment formed from materialhaving a relatively low coefficient of friction adaptEd for guiding athread in contact with said segment; means rotatably supporting saidtubular section; thread guide means disposed adjacent each mouth of saidrotary twisting member; said thread guide means connected to said meansrotatably supporting said tubular section.
 12. A rotary twisting memberaccording to claim 11 wherein said annular segments formed from materialhaving relatively low coefficient of friction are disposed on oppositesides of said annular segment formed from material having a relativelyhigh coefficient of friction.
 13. A rotary twisting member according toclaim 12 wherein said contacting surface is convex in cross section. 14.A device for false twisting threads comprising: a plurality of rotarytwisting members for imparting a twisting force to threads in contactwith the twisting member when it rotates, each of said rotary twistingmembers comprising: flange means extending in the plane of rotation ofsaid twisting member; an annular thread contacting surface having aplurality of annular segments peripherally disposed on said flange meansincluding: an annular segment formed from material having a relativelyhigh coefficient of friction, adapted to impart twisting forces tothread in contact with said segment; an annular segment formed frommaterial having a relatively low coefficient of friction adapted forguiding a thread in contact with said segment; said annular threadcontacting surfaces of said plurality of rotary twisitng members havingparallel axis of rotation.
 15. The device for false twisting threadsaccording to claim 14 wherein: said plurality of friction disc comprise:at least three mutually overlapping friction discs; the axis of rotationof said three mutually overlapping friction discs disposed to form thecorners of a substantially equilateral triangle; the contact surfaces ofsaid plurality of friction discs coacting to cause thread passingthrough said false twisting device to travel on a substantially helicalpath.
 16. The device for false twisting threads according to claim 15further comprising: a spindle; said plurality of rotary twisting membersdisposed in spaced relation on said spindle; and means to synchronouslydrive said plurality of rotary twisting members on said spindle.
 17. Thedevice for false twisting threads according to claim 16 wherein saidplurality of rotary twisting members are disposed on three spindlespositioned to form, in the plan view, a substantially equilateraltriangle.
 18. The device for false twisting threads according to claim16 wherein the coefficient of friction of said annular segments formedfrom material of a relatively high coefficient of friction varies inpredetermined relationship for said friction discs spaced along saidspindle.
 19. The device for false twisting threads according to claim 17wherein the spacing between said friction discs spaced on said spindlevaries in a predetermined relationship.
 20. The device for falsetwisting threads according to claim 17 wherein the thickness of saidflange means of said friction discs mounted in spaced relation on saidcommon spindle varies along the spindle in accordance with apredetermined relationship.